A single-frame velocity deambiguating method and device for FMCW radar

Abstract

The application discloses a single-frame velocity deblurring method and device of FMCW radar, and belongs to the technical field of radar signal processing, the method comprises the following steps: selecting a continuous linear frequency modulation signal transmitted by a transmitting antenna; performing 2DFFT processing on a received echo signal to calculate a blurred velocity estimation value; performing fast time dimension 1DFFT processing on the echo signal to calculate a plurality of distance estimation values; performing linear fitting on all the distance estimation values to obtain a curve slope, which is a target velocity estimation value; using the target velocity estimation value obtained by the curve slope, the blurred velocity estimation value obtained by 2DFFT processing and a maximum unblurred velocity to calculate a blurring multiple; and using the blurring multiple, the maximum unblurred velocity and the blurred velocity estimation value to calculate a real velocity of a target, so as to realize velocity deblurring. The application uses fast time dimension DFFT to perform velocity deblurring, without changing the working mode of the radar, and has small system operation amount and low calculation complexity.

Description

A method and apparatus for single-frame velocity deambiguation of FMCW radar Technical Field

[0001] This invention belongs to the field of radar signal processing technology, and more specifically, relates to a single-frame velocity deblurring method and apparatus for FMCW radar. Background Technology

[0002] Linear Frequency Modulated Continuous Wave (LFMCW) radar is increasingly widely used in short-range, high-resolution applications due to its small size, light weight, simple structure, high resolution, and absence of blind spots. In LFMCW radar systems, the transmitted waveform mostly uses multi-period LFMCW signals, and signal processing employs two-dimensional FFT to obtain the target's range and velocity spectrum.

[0003] Velocity ambiguity refers to the phenomenon where, when pulse Doppler radar operates at a low to medium repetition frequency (PRF), the Doppler response of observed moving targets exceeds one PRF range, resulting in ambiguity. The target velocity resolved using the ambiguous Doppler is incorrect, making it difficult to distinguish the target's true velocity.

[0004] Currently, there are many velocity deambiguation methods commonly used for Frequency Modulated Continuous Wave (FMCW) modulation. Among them, algorithms for deambiguation using multi-frequency PRF (Pulse Resonance Frequency) modulation estimate multiple sets of range and velocity parameter data based on transmitting multiple coprime sweep frequency FMCW waveforms; then, they perform matching deambiguation using algorithms such as the Sun Tzu Theorem, CRT (Continuous Frequency Resonance) algorithm, and clustering algorithm. Another velocity deambiguation algorithm inserts a time-delayed waveform sequence into the original transmitted FMCW signal, and then uses the two ambiguous velocity estimates of the same target to solve for the true velocity value of the target. In this process, the multiple estimations of velocity and range parameters and velocity matching result in a large computational load and high complexity. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a single-frame velocity deblurring method and apparatus for FMCW radar. Its purpose is to utilize fast time-dimensional FFT for velocity deblurring without altering the radar's operating mode or requiring complex transmitted frequency modulation signal patterns. This solves the technical problems of high computational load and computational complexity in existing velocity deblurring methods.

[0006] To achieve the above objectives, according to one aspect of the present invention, a single-frame velocity deblurring method for FMCW radar is provided, comprising:

[0007] S1: Select the transmitting antenna to transmit a continuous linear frequency-modulated signal;

[0008] S2: Perform 2DFFT processing on the echo signal received by the receiving antenna; the echo signal is the frequency-modulated signal emitted by the transmitting antenna reflected back from the target.

[0009] S3: Perform target detection on the 2DFFT processing results and calculate the fuzzy velocity estimate V. a ;

[0010] S4: Perform fast time-dimensional 1DFFT processing on the echo signal; use a method to improve the distance dimension resolution to ensure that the distance of the target movement within one frame must change at least once during the fast time-dimensional 1DFFT processing;

[0011] S5: Perform target detection on the 1DFFT processing results and calculate the distance estimate R corresponding to each of the frequency modulation signals. k ;

[0012] S6: Perform a linear fit on all the distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r ;

[0013] S7: The target velocity estimate V obtained using the slope of the curve. r The fuzzy velocity estimate V obtained by 2DFFT processing a and the maximum unambiguous speed V max Calculate the fuzzy factor K;

[0014] S8: Utilizing the fuzziness factor K and the maximum unfuzzy speed V max and fuzzy velocity estimate V a Calculate the true velocity of the target to achieve velocity deambiguity.

[0015] In one embodiment, S5 includes:

[0016] Target detection is performed on the 1DFFT processing result to obtain the position J of the target in the fast time dimension 1DFFT result. k ;

[0017] Using formula According to the position J k Distance resolution And the distance estimate R corresponding to each frequency modulation signal is calculated from the M value. k c is the speed of light, and B is the bandwidth of the frequency-modulated signal.

[0018] In one embodiment, S6 includes: performing a linear fit on all the distance estimates using the least squares method to obtain the slope of the fitted curve, which is the target velocity estimate V. r .

[0019] In one embodiment, the target velocity estimate V is solved using the least squares method. r The formula is:

[0020]

[0021] Where N represents the number of FM signals transmitted in each frame. The distance estimate R represents... k average value, Representing time t k The average value, t k = kT, where k is the sequence number and T is the repetition period of the transmitted FM signal.

[0022] In one embodiment, S7 includes:

[0023] Based on formula Using the target velocity estimate V r The fuzzy velocity estimate V a and the maximum unambiguous speed V max Calculate the fuzzy factor K;

[0024] in, ΔV represents velocity resolution. T represents the repetition period of the transmitted FM signal, f0 is the starting frequency of the transmitted FM signal, N represents the number of FM signals transmitted in each frame, and c is the speed of light.

[0025] In one embodiment, S8 includes:

[0026] Using V=V a +2KV max Calculate the true velocity V of the target.

[0027] In one embodiment, step S4 employs zero-padding to improve distance resolution, setting the number of FFT points to M times the number of sampling points L, where M is a positive integer; and setting... So that the distance the target moves within a frame must change at least once during fast time dimension 1DFFT processing;

[0028] in, c is the speed of light, B is the bandwidth of the frequency-modulated signal, and N represents the number of frequency-modulated signals transmitted in each frame. f0 is the starting frequency of the transmitted FM signal.

[0029] According to another aspect of the present invention, a single-frame velocity deblurring device for an FMCW radar is provided, comprising:

[0030] The antenna selection module is used to select the transmitting antenna to transmit a continuous linear frequency-modulated signal;

[0031] The 2DFFT processing module is used to perform 2DFFT processing on the echo signal received by the receiving antenna; the echo signal is the frequency-modulated signal emitted by the transmitting antenna reflected back from the target.

[0032] The first calculation module is used to perform target detection on the 2DFFT processing results and calculate the fuzzy velocity estimate V. a ;

[0033] The 1DFFT processing module is used to perform fast time-dimensional 1DFFT processing on the echo signal; a method to improve the distance dimension resolution is used to ensure that the distance of the target movement within one frame must change at least once during the fast time-dimensional 1DFFT processing;

[0034] The second calculation module is used to perform target detection on the 1DFFT processing results and calculate the distance estimate R corresponding to each of the frequency modulation signals. k ;

[0035] The linear fitting module is used to perform linear fitting on all the distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r ;

[0036] The third calculation module is used to obtain the target velocity estimate V using the slope of the curve. r The fuzzy velocity estimate V obtained by 2DFFT processing a and maximum unambiguous speed V max Calculate the fuzzy factor K;

[0037] The fourth calculation module is used to utilize the fuzziness factor K and the maximum unfuzzy speed V. max and fuzzy velocity estimate V a Calculate the true velocity of the target to achieve velocity deambiguity.

[0038] According to another aspect of the present invention, an FMCW radar system is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0039] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0040] Overall, compared with the prior art, the technical solutions conceived in this invention innovatively utilize fast time dimension FFT to provide a simpler and more effective speed deblurring scheme. It does not require changes to the radar's operating mode or complex transmitted frequency modulation signal patterns. It only requires subsequent processing to extract effective feature information for speed deblurring, reducing hardware implementation complexity and providing reliable assurance for parameter estimation and further operation of the entire system. Attached Figure Description

[0041] Figure 1 is a diagram of the velocity defuzzification algorithm for a linear frequency modulated continuous wave radar system.

[0042] Figure 2 is the time-frequency diagram of the FMCW radar sawtooth wave modulation signal;

[0043] Figure 3 is a schematic diagram of the Doppler-distance plane after 2DFFT processing;

[0044] Figure 4 is a schematic diagram of the distance dimension after 1DFFT processing. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] This invention provides a velocity deambiguation method suitable for linear frequency modulated continuous wave radar systems, as shown in Figure 1, comprising the following steps:

[0047] Step S1: Select a continuous linear frequency modulated signal transmitted by a transmitting antenna as the processing signal for subsequent steps;

[0048] The conventional FMCW-modulated millimeter-wave radar waveform consists of a series of identical linear frequency modulated (LFM) signal waveforms. In a time-division multiple-input multiple-output (TDM-MIMO) virtual aperture mode, each transmitting antenna sequentially transmits the same LFM signal multiple times. As shown in Figure 2, as an example and not a limitation, step S1 is implemented using the LFM signal transmitted by transmitting antenna TX1 out of three transmitting antennas TX1, TX2, and TX3. It is easy to understand that in this application, the LFM signal transmitted by transmitting antennas TX2 or TX3 can also be selected, and more transmitting antennas can be introduced, following the multiple-input multiple-output virtual aperture mode. Thus, the time T of one cycle is N. TX T c , where N TX T represents the number of transmitting antennas. cThis represents the duration of a single linear frequency modulated (LFM) signal. For example, a radar transmits 16 sawtooth wave signals with a repetition period T of 105 µs per frame.

[0049] Step S2: Perform 2DFFT processing on the signal received by the receiving antenna from the transmitting antenna after reflection by the target;

[0050] In one embodiment, the received signal is mixed to obtain an intermediate frequency (IF) signal, which is then sampled by an ADC and processed by a 2DFFT.

[0051] The expression for the intermediate frequency signal y(t) is as follows:

[0052]

[0053] t k =kT#(2)

[0054] Where T is the signal repetition period, for example, set to 105µs, and f0 is the starting frequency of the transmitted FM signal, assumed to be 77GHz. s This represents the slope of the frequency modulation signal, assumed to be 12*10. 13 Hz / s, τ k Let represent the time delay caused by the k-th (0≤k≤15) transmitted FM signal, and its expression is:

[0055]

[0056] The intermediate frequency signal is then sampled by the ADC, and the sampling frequency is set to f. s =12.5MHz, number of sampling points L=256.

[0057] Step S3: Perform target detection on the 2DFFT processing results to obtain the target's position in the Doppler-range 2DFFT results. Calculate the blurred velocity estimate V based on the position and velocity resolution. a ;

[0058] V a The expression is as follows:

[0059] V a =IΔV#(4)

[0060] Where I represents the target's position index in the Doppler-range 2DFFT result, as shown in Figure 3, and ΔV represents the velocity resolution, the expression of which is as follows:

[0061]

[0062] Where T is the signal repetition period, set to 105µs, f0 is the starting frequency of the transmitted FM signal, set to 77GHz, N represents the number of FM signals transmitted in each frame, set to 16, and c is the speed of light.

[0063] Step S4: For the signal received by the receiving antenna and reflected by the target from the transmitting antenna, a method to improve the distance dimension resolution is used to ensure that the distance of the target's movement within one frame must change at least once during fast time dimension 1DFFT processing;

[0064] In one embodiment, the received signal is mixed to obtain an intermediate frequency (IF) signal. This IF signal is then sampled by an ADC and subjected to a 1D FFT (First-Degree Fourier Transform). The number of FFT points is set to M times the number of sampling points. The value of M must ensure that the target's distance movement within one frame changes at least once during the fast-time 1D FFT processing. It should be noted that zero-padding is used here to improve range resolution. Other methods to improve range resolution, such as CZT (Concurrent-Zero Transform), can also be used, but the chosen method must ensure that the number of sampling points corresponding to the echo signal guarantees that the target's distance movement within one frame changes at least once during the fast-time 1D FFT processing.

[0065] Step S5: Perform target detection on the 1DFFT processing results to obtain the target's position in the fast time dimension 1DFFT result. Calculate each distance estimate R based on the position, distance resolution, and M value. k ;

[0066] Distance estimate R k The expression is as follows:

[0067]

[0068] Among them, J k The position index of the target in the fast time dimension 1DFFT result is shown in Figure 4. ΔR represents the range resolution, and its expression is as follows:

[0069]

[0070] Step S6: Perform linear fitting on all obtained distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r ;

[0071] In one embodiment, 16 distance estimates were obtained, and a linear fit was performed using the least squares method to obtain the slope of the fitted curve, which is the target velocity estimate V. r .

[0072] The target velocity estimate V is obtained using the least squares method. rThe formula is as follows:

[0073]

[0074] Where N represents the number of FM signals transmitted in each frame; for example, N is 16. The distance estimate R represents... k average value, Representing time t k Average value:

[0075]

[0076]

[0077] Step S7: In one embodiment, the target velocity estimate V obtained from the slope of the curve is... r Subtract the fuzzy velocity estimate V calculated by 2DFFT in step S3. a Then, divide by the maximum unambiguous speed V max Twice (positive or negative) and rounded to the nearest integer, we obtain the fuzzy multiple K, which is expressed as follows:

[0078]

[0079] The expression for the maximum unambiguous speed is as follows:

[0080]

[0081] Step S8: Multiply the blur factor K by the maximum unblurring speed V. max Double the value of the fuzzy velocity estimate V calculated by 2DFFT in step S3. a The velocity ambiguity can then be resolved to obtain the target's true velocity V, expressed as follows:

[0082] V = V a +2KV max #(13)

[0083] The description uses the FFT to increase the number of points to improve range resolution. The value of M cannot be too small. The true velocity of the target is exactly the maximum unblurred velocity V. max In this case, the distance the target moves within one frame must change at least once during fast time dimension 1DFFT processing; otherwise, the target velocity cannot be accurately calculated. That is, M must satisfy the following formula:

[0084]

[0085] Simplifying, we get:

[0086]

[0087] For example, ΔR = 0.061m, N = 16. Meanwhile, M can be an integer, and the minimum value of M is calculated to be 4.

[0088] In one embodiment, the initial target distance is set to 0.15m, the target's actual velocity is set to 45m / s, M is set to a minimum value of 4, and the maximum unambiguous velocity V is set to... max The velocity is 9.276 m / s. The fuzzy velocity estimate V calculated using this method is... a The value is 8.117 m / s, the ambiguity factor K is 2, and the target velocity V is 45.221 m / s. The error is very small compared with the set target actual velocity, which shows the correctness of the method.

[0089] According to another aspect of the present invention, a single-frame velocity deblurring device for FMCW radar is provided, comprising:

[0090] The antenna selection module is used to select the transmitting antenna to transmit a continuous linear frequency-modulated signal;

[0091] The 2DFFT processing module is used to perform 2DFFT processing on the echo signal received by the receiving antenna; the echo signal is the frequency-modulated signal emitted by the transmitting antenna reflected back from the target.

[0092] The first calculation module is used to perform target detection on the 2DFFT processing results and calculate the fuzzy velocity estimate V. a ;

[0093] The 1DFFT processing module is used to perform fast time-dimensional 1DFFT processing on the echo signal; a method to improve the distance dimension resolution is used to ensure that the distance of the target movement within one frame must change at least once during the fast time-dimensional 1DFFT processing;

[0094] The second calculation module is used to perform target detection on the 1DFFT processing results and calculate the distance estimate R corresponding to each of the frequency modulation signals. k ;

[0095] The linear fitting module is used to perform linear fitting on all the distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r ;

[0096] The third calculation module is used to obtain the target velocity estimate V using the slope of the curve.r The fuzzy velocity estimate V obtained by 2DFFT processing a and maximum unambiguous speed V max Calculate the fuzzy factor K;

[0097] The fourth calculation module is used to utilize the fuzziness factor K and the maximum unfuzzy speed V. max and fuzzy velocity estimate V a Calculate the true velocity of the target to achieve velocity deambiguity.

[0098] According to another aspect of the present invention, an FMCW radar system is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0099] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0100] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A single-frame velocity deambiguation method for FMCW radar, characterized in that, include: S1: Select the transmitting antenna to transmit a continuous linear frequency-modulated signal; S2: Perform 2DFFT processing on the echo signal received by the receiving antenna; The echo signal is the frequency-modulated signal emitted by the transmitting antenna reflected back from the target. S3: Perform target detection on the 2DFFT processing result and calculate the fuzzy velocity estimate V. a S4: Perform fast time-dimension 1DFFT processing on the echo signal; use a method to improve the range dimension resolution to ensure that the distance of the target movement within one frame must change at least once during the fast time-dimension 1DFFT processing; S5: Perform target detection on the 1DFFT processing results and calculate the range estimate R corresponding to each of the frequency modulation signals. k S6: Perform a linear fit on all the distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r S7: The target velocity estimate V obtained using the slope of the curve. r The fuzzy velocity estimate V obtained by 2DFFT processing a and the maximum unambiguous speed V max Calculate the fuzziness factor K; S8: Use the fuzziness factor K and the maximum unfuzzy speed V max and fuzzy velocity estimate V a Calculate the true velocity of the target to achieve velocity deambiguity.

2. The single-frame velocity deambiguation method for FMCW radar as described in claim 1, characterized in that, S5 includes: performing target detection on the 1DFFT processing result to obtain the position J of the target in the fast time dimension 1DFFT result. k Using formulas According to the position J k Distance resolution And the distance estimate R corresponding to each frequency modulation signal is calculated from the M value. k c is the speed of light, and B is the bandwidth of the frequency-modulated signal.

3. The single-frame velocity deambiguation method for FMCW radar as described in claim 1, characterized in that, S6 includes: using the least squares method to perform linear fitting on all the distance estimates, and obtaining the slope of the fitted curve as the target velocity estimate V. r .

4. The single-frame velocity deambiguation method for FMCW radar as described in claim 3, characterized in that, The target velocity estimate V is obtained using the least squares method. r The formula is: Where N represents the number of FM signals transmitted in each frame. The distance estimate R represents... k average value, Representing time t k The average value, t k = kT, where k is the sequence number and T is the repetition period of the transmitted FM signal.

5. The single-frame velocity deambiguation method for FMCW radar as described in claim 1, characterized in that, S7 includes: based on the formula Using the target velocity estimate V r The fuzzy velocity estimate V a and the maximum unambiguous speed V max Calculate the fuzzy factor K; where, ΔV represents velocity resolution. T represents the repetition period of the transmitted FM signal, f0 is the starting frequency of the transmitted FM signal, N represents the number of FM signals transmitted in each frame, and c is the speed of light.

6. The single-frame velocity deambiguation method for FMCW radar as described in claim 5, characterized in that, S8 includes: utilizing V = V a +2KV max Calculate the true velocity V of the target.

7. The single-frame velocity deambiguation method for FMCW radar as described in claim 1, characterized in that, In step S4, zero-padding is used to improve distance resolution. The number of FFT points is set to M times the number of sampling points L, where M is a positive integer; and the following settings are made: So that the distance the target moves within one frame must change at least once during fast time dimension 1DFFT processing; where, c is the speed of light, B is the bandwidth of the frequency-modulated signal, and N represents the number of frequency-modulated signals transmitted in each frame. f0 is the starting frequency of the transmitted FM signal.

8. A single-frame velocity de-ambiguity device for FMCW radar, characterized in that, include: The antenna selection module is used to select the transmitting antenna to transmit a continuous linear frequency-modulated signal; The 2DFFT processing module is used to perform 2DFFT processing on the echo signal received by the receiving antenna. The echo signal is the frequency-modulated signal emitted by the transmitting antenna reflected back from the target. The first calculation module is used to perform target detection on the 2DFFT processing results and calculate the fuzzy velocity estimate V. a The first 1DFFT processing module performs fast time-dimension 1DFFT processing on the echo signal; it employs a method to improve range dimension resolution to ensure that the target's moving distance within one frame must change at least once during the fast time-dimension 1DFFT processing; the second calculation module performs target detection on the 1DFFT processing results and calculates the range estimate R corresponding to each of the frequency modulation signals. k ; The linear fitting module is used to perform linear fitting on all the distance estimates to obtain the slope of the curve, which corresponds to the target velocity estimate V. r The third calculation module is used to obtain the target velocity estimate V using the slope of the curve. r The fuzzy velocity estimate V obtained by 2DFFT processing a and maximum unambiguous speed V max Calculate the fuzziness factor K; the fourth calculation module is used to calculate the fuzziness factor K and the maximum unfuzzy speed V. max and fuzzy velocity estimate V a Calculate the true velocity of the target to achieve velocity deambiguity.

9. An FMCW radar system, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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